Defect, Failure, Error, and Root Cause
1. Introduction
One of the most important topics in the ISTQB Foundation Level exam is understanding the difference between error, defect, failure, and root cause.
This question presents a realistic scenario involving design mistakes, programming under pressure, and real-world consequences.
ISTQB 시험에서 가장 중요한 개념 중 하나는 오류(Error), 결함(Defect), 실패(Failure), 근본 원인(Root Cause)의 차이를 정확히 구분하는 것입니다.
2. Practice Question
❓ Question
A designer documents a user interface design that does not suitably address disabled users. The programmer implements the design but, due to severe time pressure, does not include proper exception handling for bonus calculations.
When the system is used:
- Complaints are made by disabled users
- The company is fined by a regulatory authority
- No one notices that bonus calculations are sometimes incorrect
Which of the following statements is CORRECT?
- a) The miscalculation of bonuses is a defect that occasionally occurs
- b) The fine received for failing to address some disabled users is a failure
- c) The programmer working under severe time pressure is a root cause
- d) The design of the user interface includes a designer error
✅ Correct Answer: c)
3. Explanation
✔ c) The programmer working under severe time pressure is a root cause — Correct
The programmer makes a mistake by not implementing proper exception handling.
The underlying reason for this mistake is severe time pressure, which is the root cause of the defect.
프로그래머는 예외 처리를 구현하지 않는 오류(Error)를 저질렀습니다.
그 근본적인 이유는 심각한 일정 압박이며, 이는 결함을 유발한 근본 원인(Root Cause)입니다.
❌ a) The miscalculation of bonuses is a defect that occasionally occurs — Incorrect
Incorrect bonus calculation is an observable incorrect behavior of the system.
This is a failure, not a defect.
보너스 계산이 잘못되는 것은 시스템이 잘못 동작한 결과로, 실패(Failure)입니다.
결함(Defect)은 코드나 설계 내부에 존재하는 문제를 의미합니다.
❌ b) The fine received for failing to address some disabled users is a failure — Incorrect
The system failing to support disabled users is a failure.
However, the fine itself is not a failure of the system. It is the correct functioning of the regulatory process.
장애 사용자를 제대로 지원하지 못한 것은 시스템 실패이지만,
그 결과로 받은 벌금은 시스템 실패가 아니라 규제 기관이 정상적으로 동작한 결과입니다.
❌ d) The design of the user interface includes a designer error — Incorrect
The designer made an error, which resulted in a design defect.
The design contains a defect, not an error. Errors are human actions, not artifacts.
디자이너의 오류(Error)로 인해 UI 설계에 결함(Defect)이 포함되었습니다.
설계 문서는 오류가 아니라 결함을 포함합니다.
4. Summary Table
| Concept | Scenario Example | Correct Term | 요약 |
|---|---|---|---|
| Error | Programmer forgets exception handling | Error | 사람의 실수 |
| Root Cause | Severe time pressure | Root Cause | 근본 원인 |
| Defect | Missing exception handling in code | Defect | 코드 결함 |
| Failure | Incorrect bonus calculation | Failure | 시스템 오동작 |
5. Final Takeaway
For the ISTQB exam, always remember the chain:
Root Cause → Error → Defect → Failure
시험 대비 핵심 흐름입니다.
근본 원인 → 오류 → 결함 → 실패
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